What is the incidence and management of diffuse pulmonary meningiotheliomatosis?

Diffuse Pulmonary Meningotheliomatosis: Incidence and Management

Diffuse pulmonary meningotheliomatosis (DPM) is an exceedingly rare entity with fewer than 15 documented cases in the medical literature, primarily affecting middle-aged to elderly women and characterized by multiple minute pulmonary meningothelial-like nodules throughout both lungs. 1, 2, 3

Epidemiology and Demographics

• DPM is extremely rare with only approximately 11 documented cases reported in the literature as of 2019 3
• Strong female predominance (10 out of 11 reported cases were women) 3
• Age range: 51-75 years, with mean age of 64±8 years 3
• Most patients (8 out of 11) had no history of smoking or occupational exposure 3

Clinical Presentation

• Patients may be asymptomatic with incidental findings on imaging 4
• When symptomatic, presentations include:
  • Dyspnea, shortness of breath, or fatigue (7 out of 11 cases) 3
  • Non-exertional chest pressure and dry cough 2
  • Intermittent cough and expectoration 3
• Mild abnormalities on pulmonary function testing are common (8 out of 11 cases) 3

Radiological Features

• Characteristic findings on chest CT:
  • Innumerable diffuse small ground-glass nodules 2
  • Randomly distributed, bilateral small solid or ground-glass nodules <5mm in diameter 3
  • Some nodules may demonstrate cavitation 3, 4
  • Miliary pattern resembling tuberculosis or metastatic disease 4

Diagnostic Approach

• Definitive diagnosis requires histopathological confirmation:

  • Open lung biopsy (8 of 11 cases) 3
  • Transbronchial lung biopsy (2 of 11 cases) 3, 5
  • CT-guided fine needle aspiration (1 case) 1, 3

• Cytological features include:

  • Whorled/nested clusters of elongated cells
  • Oval nuclei with clear pseudonuclear inclusions
  • Nuclear grooves/indentations
  • Smooth nuclear contours
  • Fine granular chromatin
  • Abundant fibrillary cytoplasm with indistinct cell borders 1

• Histopathological features:

  • Multiple well-circumscribed interstitial meningothelial-like nodules
  • Perivenular distribution
  • Occasional whorling of cells 2

Differential Diagnosis

DPM should be included in the differential diagnosis for patients presenting with diffuse bilateral pulmonary nodules, particularly with a miliary pattern. Other conditions to consider:

• Miliary tuberculosis
• Metastatic cancer
• Sarcoidosis
• Hypersensitivity pneumonitis
• Pneumoconiosis 2, 4

Natural History and Management

• DPM appears to have a benign clinical course
• No specific treatment is currently recommended
• Observation with periodic follow-up imaging is appropriate
• In the limited follow-up data available (3 patients followed for 12-92 months), lung lesions remained stable 3
• One patient showed stable findings on repeat chest CT one year after diagnosis 2

Key Clinical Pearls

• DPM should be considered in the differential diagnosis of diffuse bilateral pulmonary nodules, especially in middle-aged to elderly women
• Transbronchial biopsy can establish the diagnosis and avoid more invasive surgical procedures 5
• Despite the extensive radiographic appearance, the condition appears to have a benign clinical course
• The condition is often misdiagnosed initially due to its rarity and radiographic similarity to more common conditions like tuberculosis or metastatic disease
• No specific treatment is currently indicated, and observation with periodic imaging is appropriate for most patients

Research Gaps

• The etiology and pathogenesis of DPM remain unclear
• Long-term follow-up data are limited
• No established guidelines exist for management due to the rarity of the condition
• Further research is needed to better understand the natural history and clinical significance of this rare entity